This invention relates generally to fuel injection systems for internal combustion engines, and more particularly to a fuel injection pump of a fuel injection system for controlling fuel flow rate supplied to cylinders of a diesel engine.
Conventional distribution type fuel injection pumps are widely used for diesel engines because of their simple structure and small size. Such conventional fuel injection pumps are divided into two sorts the axially movable and rotatable plunger type and the inner cam type having plungers radially received in a rotor. In the former type pump, the fuel is apt to be forcibly introduced into a compression chamber via a relatively narrow passage because the plunger reciprocates in timed relation to engine rotation. As a result, air bubbles are readily introduced into the fuel in the compression chamber. In the latter type pump, since the plungers are apt to move radially outwardly due to centrifugal force, air bubbles are readily introduced into fuel in the compression chamber. Such air bubbles mixed in compressed fuel raise various problems. Namely, accurate fuel amount cannot be ensured, and thus irregular fuel injection is apt to occur.